No cause of death has been disclosed for Dianne Feinstein, the longtime California senator who struggled with evident health problems in her final years before her death Thursday night.

She was absent from the U.S. Senate for nearly three months earlier this year while recovering from a case of shingles that led to encephalitis, a rare complication that causes inflammation and swelling in the brain. She was briefly hospitalized in August after falling at her home and was often seen in a wheelchair in public.

Indications that Feinstein, 90, was struggling with memory problems have persisted for years, even before the acknowledged health crises in the last year of her life.

Several of Feinstein’s colleagues and former staffers confided to reporters that she was often unable to recognize longtime colleagues and repeated herself frequently. In July she appeared confused during a Senate Appropriations Committee vote and began to read a prepared statement before the committee chair prompted her to “just say aye.”

Feinstein maintained that she was cognitively fit to continue her fifth full term, and neither her office nor her family has ever confirmed if she had any neurological condition.

Even if the senator’s apparent memory lapses were the result of dementia, the disease would almost certainly not have been her cause of death, doctors said Friday.

“In general, older adults often have a confluence of several different medical problems, and to say which one, ‘caused the death’ can be very difficult,” said Dr. Laura Mosqueda, a professor of geriatrics and family medicine at USC Keck School of Medicine. “We don’t need to look for a simple answer to an actually complicated question.”

The most common cause of dementia is Alzheimer’s disease, a progressive and incurable condition. Alzheimer’s can be a direct cause of death in its latest stages, when the disease begins to damage parts of the brain that control essential biological functions like breathing and swallowing.

A common cause of death for people with late-stage Alzheimer’s is aspiration pneumonia, an infection in the lungs triggered by food or other foreign substance that goes down the windpipe instead of the esophagus. This becomes a bigger risk as the muscles that control swallowing and chewing weaken in the late stages of the disease.

By then, it is no longer possible for patients to keep up even a semblance of their previous activities.

“You would typically not see someone functioning, walking, talking. Usually people are bedridden at that point,” said Dr. Mark Mapstone, a neuropsychologist at UC Irvine.

Doctors were quick to note that without knowing Feinstein’s health history, it was impossible to know for certain whether she suffered from any neurological condition.

Yet even though her appearance in the Senate in her final years was a shock to those familiar with her during her long career, she was not as ill as a person with advanced Alzheimer’s.

“Dianne Feinstein was looking pretty frail and seemed a little confused sometimes in public appearances,” said Dr. Michael Weiner of UC San Francisco, the principal investigator of the Alzheimer’s Disease Neuroimaging Initiative. Yet if she did have dementia, he said, “she was definitely not in an advanced stage. It wasn’t even clear if you can say she was in a moderate stage. You can only judge from these outside appearances.”

To anyone who has paid even a modicum of serious attention to COVID-19 and its treatment, ivermectin is the zombiest of zombie drugs.

Used to treat parasitic diseases in animals and humans, the drug became a darling of anti-vaccination activists and conspiracy-mongers, who pushed it as a treatment for the pandemic disease and claimed it was being suppressed by Big Pharma, among other sinister forces.

Contrary to its continued promotion by quacks such as Florida Surgeon General Joseph Ladapo, the drug has been conclusively shown to be utterly useless against COVID.

One would have hoped that hard scientific evidence and a stern advisory by the Food and Drug Administration against its use would have been enough to kill the ivermectin craze, but it lives on. Last year, three doctors sued the FDA, claiming that its public warning harmed their practices and cost them their jobs at hospitals and medical schools.

A few months later, a federal judge in Galveston threw out their case, ruling in effect that they didn’t come close to having a leg to stand on. That should have been an end to it. But earlier this month, the case was revived by the U.S. 5th Circuit Court of Appeals, which takes cases from Texas, Louisiana and Mississippi and is, by many measures, the hackiest of hack-ridden federal courts.

The three judges hearing this appeal — two appointed by George W. Bush and one (the opinion’s author) by Donald Trump — found that the FDA had exceeded its authority in advising against the use of ivermectin against COVID. “The FDA can inform,” the court said, “but it has identified no authority allowing it to recommend consumers ‘stop’ taking medicine.” (Emphasis in the original.)

That’s absurd, says Dorit Rubinstein Reiss, an expert on vaccine policy at University of California College of the Law, San Francisco, and the author of a withering analysis of the 5th Circuit opinion.

The FDA’s job, Reiss told me, is to “balance the need for treatment with safety concerns. If the FDA can’t translate what it’s finding into plain language — ‘do this, don’t do that’ — then it can’t do its job. That undermines the whole regulatory scheme.”

More on that in a moment. First, some context.

Undermining the FDA’s authority has been a right-wing project for years. That’s because the agency’s duty is to stand in the way of businesses desiring to push unsafe and ineffective nostrums at unwary consumers, and also in the way of a perverse idea that personal freedom includes the freedom to be gulled by charlatans.

This campaign got pumped up during the Trump administration. Trump in 2018 signed a federal “right-to-try” law that masqueraded as a compassionate path giving sufferers of intractable, incurable diseases access to experimental treatments. In fact, as I wrote, it was a cynical ploy backed by the Koch brothers’ network aimed at emasculating the FDA in a way that would undermine public health.

Trump subsequently browbeat his maladroit FDA chairman, Stephen Hahn, into issuing an emergency authorization for the use of convalescent plasma to treat COVID-19 patients. Like ivermectin, that was another utterly ineffective treatment.

In announcing his decision while Trump stood glaring at him, Hahn grossly misrepresented the results of a medical trial conducted by the Mayo Clinic, which failed to demonstrate any effectiveness for the treatment. In the run-up to the announcement, Trump issued a tweet accusing “the deep state … at the FDA” of deliberately delaying effective COVID treatments until after the upcoming Nov. 3, 2020, election, which Trump lost. Hahn didn’t respond to that frontal attack on his agency’s integrity.

The FDA is under more solid management now, but the malign influence of judges Trump installed in the federal judiciary lives on. That brings us to the 5th Circuit, on which 12 of the 16 currently active judges were appointed by Republican presidents — six by Trump.

The court has received appeals of some of the loopiest district court rulings of recent memory, largely because conservative litigants in Texas have the ability to hand-pick judges who see things their way.

Among the recent rulings those judges have issued that swear at precedent and common sense are those outlawing the use of the medication mifepristone for abortion (another case aimed at undermining FDA authority) and barring agencies of the federal government from communicating with social media companies, which was brought by right-wing litigants hoping to hobble the government’s battle against medical misinformation.

The 5th Circuit judges have frequently matched the district court rulings they’re reviewing with loopy opinions of their own.

Trump appointee James Ho issued a partial concurrence in the mifepristone case in which he asserted that an “unborn child” was “killed by mifepristone,” and justified outlawing use of the drug by stating that “unborn babies are a source of profound joy for those who view them. Expectant parents eagerly share ultrasound photos with loved ones. Friends and family cheer at the sight of an unborn child. Doctors delight in working with their unborn patients — and experience an aesthetic injury when they are aborted.”

(The court narrowed the FDA’s authority to approve the drug, but its ruling is under review by the Supreme Court.)

In a 2019 case, a three-judge panel voted 2-1 to find that a key provision of the Affordable Care Act, and possibly the entire law, was unconstitutional. In her concurrence, Jennifer Walker Elrod, a George W. Bush appointee in the majority, approvingly repeated a right-wing congressman’s claim that the act was “a fraud on the American people.”

The 5th Circuit judges combine their clownish approach to the law with a clownish confusion over the federal rules of procedure they are bound to apply. As recently as Tuesday, the appeals court had to withdraw an order it had issued the day before, granting red state plaintiffs a rehearing in the case involving government contacts with social media companies.

The court had originally allowed four government agencies to continue interacting with the companies; the red states wanted the judges to withdraw their permission. But the court’s granting of a rehearing so flagrantly violated procedural rules governing cases, like this one, that are already under consideration by the Supreme Court, that it had to immediately backtrack. (The circuit’s clerk of the court obligingly accepted the blame, attributing Monday’s grant to a “clerical error.”

The judges who made this blunder — Elrod, Edith Brown Clement and Don R. Willett — are the same ones who ruled in the ivermectin case. Let’s take another gander at that ruling.

Reiss terms the ruling “problematic on legal and policy grounds” by “undercutting the FDA’s ability to offer expertise-based guidance about products they regulate.”

The judges were particularly exercised by an FDA Twitter campaign that aimed to dissuade consumers from taking the veterinary preparation of ivermectin commonly administered to horses.

“You are not a horse,” the agency tweeted. “Stop it with the #ivermectin. It’s not authorized for treating #COVID.” The agency also issued a general warning headlined “Why You Should Not Use Ivermectin to Treat or Prevent COVID-19,” explaining that the drug has not been shown to be effective for the purpose and is dangerous in high doses.

The three plaintiff doctors — one from Virginia, one from Texas, and one practicing in Washington and Arizona — had lost their hospital privileges or other professional positions for promoting the drug. The latter plaintiff is under investigation by medical regulators in the two states where he’s licensed. All three blamed the FDA.

The 5th Circuit judges agreed that even though the agency pointed out that it has no power to order patients to do or not do anything and no authority over physicians — who have the legal right to prescribe medications approved by the FDA for “off-label” uses — it had exceeded its authority by using “imperative” language (i.e., “Stop it”) instead of merely declaring that the drug wasn’t approved for COVID.

Yet as Reiss points out, the FDA frequently couches its advisories in such straightforward terms, and has done so virtually since its creation in its present form in 1930. The agency’s warning against unproven stem cell treatments — a dark and dangerous hive of medical charlatans — advises patients, “Don’t believe the hype” and adds that it’s “increasing its oversight and enforcement to protect people from dishonest and unscrupulous stem cell clinics.”

Carrying the 5th Circuit’s ruling to its logical extreme, the agency’s stem cell warning would exacerbate the vulnerability of disease sufferers to quacks hawking expensive and ineffective treatments.

Despite the judges’ contention that it has no authority to offer recommendations to the public, Reiss notes that such authority is actually embedded in federal law, which gives the FDA the right to undertake “collecting, reporting, and illustrating the results of [its] investigations.”

“That certainly seems to include conclusions based on the data collected,” Reiss wrote: “Reporting on the result of an investigation that showed ivermectin is not effective for COVID-19 would naturally include a comment that it should not be used.”

In any event, there’s no case to be made that the FDA warnings caused the doctors’ professional troubles. Several professional organizations have warned of the ineffectiveness of ivermectin for COVID, including the American Medical Assn. No medical board needed the FDA to tell it that doctors prescribing this modern snake oil deserved scrutiny.

It’s possible that the appellate judges themselves had an inkling that they were on thin ice in their ruling. They didn’t rule conclusively that the FDA was wrong, but rather sent the case back to the trial court judge for further pondering on technical grounds, such as whether the FDA’s advisories amount to “final agency actions” subject to court review or whether the doctors even had standing to bring the lawsuit in the first case.

“They seem to be trying to hedge,” Reiss says. On the other hand, they didn’t dismiss the case outright, as they should have. The judges cast a shadow over the FDA, at a time when its crucial, lifesaving campaign against medical misinformation doesn’t need any more head winds.